What is a pesticide?

The definition of a pesticide encompasses a broad range of substances utilized to manage or control pests, which may include insects, weeds, fungi, rodents, and other undesirable organisms. Answering with "any substance used to prevent, destroy, repel, kill or mitigate pests" captures the comprehensive nature of what pesticides can do. This definition highlights that pesticides are not limited to certain categories but apply to various methods of pest management, acknowledging both chemical and biological agents.

Other options provided lack this holistic view; the first option restricts pesticides to substances that exclusively kill plants, which doesn't encompass the diverse range of pests that pesticides are designed to target. The third option mischaracterizes pesticides as fertilizers, which serve a different purpose by enhancing plant growth rather than managing pest populations. Lastly, the fourth option incorrectly identifies a natural agent promoting plant growth, while pesticides are specifically meant for pest control. Thus, the second option is the most accurate and widely accepted definition of pesticides in agricultural and environmental contexts.